Dr. Pepper, referred to by some as 'D.P.', is a soft drink that comes in a dark red can with white letters, which are underscored by a lighter red line. The diet version is vice-versa save for the line. The caffeine free version is an odd muted gold with the normal kind's coloring, and the caffeine free diet looks like the diet with a gold circle denoting its attributes.
Like all sodas, Dr. Pepper is difficult to adequately describe. It is not at all like Coke, or really any other soft drink. It has a very mellow, sweet, and fruity flavor, but is not like punch. It is not nearly as acidic as Coke, not as sweet as root beer, and not as over-flavored as fruit punch (has anyone else noticed that punch leaves a weird dry feeling afterwards, like it's dehydrating you?).
It goes down very smoothly, and is easy to both sip and chug. The diet has less body and a more noticeably artificial taste, but is still palatable. The caffeine free version is not consumed as often, but as best I can describe the flavor is closer to the original than diet. Diet caffeine free tastes like diet.
Dr. Pepper's flavor is very complex, leading to the '23' ads in the last few years. Unfortunately they have now slapped the number on the cases, which makes them seem odd to a regular customer.
Dr. Pepper is actually similar to Mr. Pibb (anybody remember that? It's still out there...), in that Mr. Pibb tastes a lot like DP and root beer being mixed with a tiny amount of Coke.
Like all sodas, the container makes a difference. Personally I think Dr. Pepper is better in glass bottles. Sometimes these have cane sugar in them, but they're so unfamiliar now I can't really tell you if they're better or worse. Of course, personal opinion is key. If you like it one way, enjoy it.
Dr. Pepper is a familiar face to those down South, and you may well find it an option someday soon, whether while traveling, or if it reaches your area. Either way, I suggest you give it a taste if you have the chance. Just a word of advice - don't let the first drink be Diet.
